Set the Contact Entity form read only based on other Entity field value

Hi Team,

I have a requirement where I have to make the contact entity form read only if the other entity field Contains option A, If it contains Option B it should be editable. (The Contact entity and other entity have 1:n relationship)

If it is on the same entity, I believe we can achieve through Business rule.

Any help or guidance to solve this will be highly appreciated.

Thanks.